Warming trend moves chickadee zone north

A long, narrow strip from Kansas to New Jersey where two species of chickadees mate and create
hybrid birds is moving north at a rate that matches the warming trend in winter weather, scientists
say.

“It has moved north by about 7 miles in the last 10 years,” said Scott Taylor, an evolutionary
biologist at the Cornell Lab of Ornithology at Cornell University.

The scientists, who reported their findings in the journal
Current Biology, relied on blood samples drawn from chickadees in Pennsylvania and on
sightings of hybrid chickadees.

They found that hybrids were sighted in areas where the average low temperature in winter was 15
to 19 degrees — the same readings as a decade earlier, but in a zone 7 miles north of the 2000-02
sightings.

The gene behind a butterfly disguise

A single gene controls all the colors, structures and wing patterns in a species of swallowtail
butterfly, researchers say — a trick that allows it to mimic the look of another swallowtail that
is toxic to predators.

“Everything traces back to this one gene,” said Marcus Kronforst, an evolutionary biologist at
the University of Chicago.

The finding, reported in the journal
Nature, was surprising, because the gene, called doublesex, is known for its role in
sexual differentiation in insects.

Female
Papilio polytes swallowtails have one of four wing patterns, three of which mimic the look
of different toxic butterflies.

To identify the gene responsible for regulating wing patterns, the researchers mated
swallowtails with different patterns and compared the genomes of the offspring, then isolated genes
that might be involved in mimicry.

They expected to find multiple, tightly linked genes working together. Instead, they found that
only one, doublesex, is responsible for mimicry.